1. Technical Field
The present disclosure relates to a control device and a control method for a hybrid vehicle including an automatic transmission.
2. Description of Related Art
A vehicle which travels using power of at least one of an engine and a rotating electric machine, a so-called hybrid vehicle, normally includes a high-voltage battery which stores electric power for driving the rotating electric machine, and an electric power conversion device which performs electric power conversion between the battery and the rotating electric machine. Inside the electric power conversion device, in general, a capacitor for stabilizing a voltage is provided. Since the capacitance of the capacitor is large, in a case where the vehicle collides against a collision object, such as other vehicles or obstacles, it is desirable to quickly discharge the residual electric charge of the capacitor in order to prevent the residual electric charge of the capacitor from leaking and affecting other devices.
Of the hybrid vehicles, there is a hybrid vehicle in which an automatic transmission is provided between a rotating electric machine and drive wheels. In a hybrid vehicle including an automatic transmission, if down-shift control, that is, control for increasing the ratio (the gear ratio of the automatic transmission) of an input shaft rotation speed to an output shaft rotation speed is performed at the time of a collision of the vehicle, there occurs a problem in that discharging cannot be made quickly. That is, if the down-shift control is performed at the time of the collision of the vehicle, the rotation speed of the rotating electric machine increases with an increase in the rotation speed of the input shaft of the automatic transmission. If the rotation speed of the rotating electric machine increases, since the time until the rotating electric machine is stopped is extended, and a counter electromotive force of the rotating electric machine continues to be supplied to a capacitor over a long period of time, the time required for discharging the residual electric charge of the capacitor is extended.
As a measure for the above-described problem, Japanese Patent Application Publication No. 2014-113878 (JP 2014-113878 A) discloses a technique which, in a hybrid vehicle including an automatic transmission, inhibits down-shift control in a case where a collision of the vehicle is detected. According to this technique, after the collision of the vehicle, an increase in the rotation speed of the rotating electric machine due to the down-shift control is suppressed. For this reason, the extension of the time required for discharging the residual electric charge of the capacitor is suppressed.